Adolescents and Gender
For almost everyone, puberty is a phase of discomfort with one's own body. Breast development, menstruation, facial hair, voice changes, acne, sexual feelings, doubts about one's place in the group — all of it is part of the process. The Cass Review describes puberty as a period of intense, rapid change in which young people are vulnerable to mental health problems, especially girls, and writes that unwanted physical changes can be uncomfortable for all young people (source). A teenager temporarily feeling alienated from their own body is therefore not, in itself, an indication of having been born the wrong sex.
A sharp rise in referrals — and no single explanation
According to the Cass Review, the British gender clinic GIDS saw fewer than 50 children a year before 2009. From 2014 onwards referrals rose exponentially; in 2021/22 there were about 5,000, with the caveat that this may include double counting. The majority of referrals concerned girls presenting in their early teens, whereas in the early years it was mainly pre-pubertal children who were referred. Referrals also rose in other countries; in the Netherlands the increase began in 2001, with a turning point in 2011 (source). See also the growth in referrals in the Netherlands.
The Cass Review writes that there is no single explanation for the increase: all of the proposed explanations probably play a part to a greater or lesser extent, and the mix is different for every young person. The report mentions, among other things, the influence of social media and peers, and writes that it heard stories of girls at school who formed intense friendships with other young people who were questioning whether they were trans and who then went on to identify as trans themselves (same source). See also Social Media and Gender and Rapid Onset Gender Dysphoria.
Cass Review: the evidence base is weak
The Cass Review (Hilary Cass, 2024) is an independent review commissioned by NHS England. In her foreword, Cass calls this 'an area of remarkably weak evidence' (Cass Review (full report)). The systematic reviews by the University of York for the report assessed 50 studies on puberty suppression (1 of high, 25 of moderate and 24 of low quality) and 53 studies on cross-sex hormones (1 of high, 33 of moderate and 19 of low quality). For puberty blockers, the evidence on the effect on gender dysphoria and mental health was limited or contradictory; for hormones, the review found indications that mental health may improve, but robust research with long-term follow-up is lacking (York, puberty suppression; Cass Review).
On the claim that treatment prevents suicide, the Cass Review writes that the evidence does not adequately support the claim that gender-affirming treatment reduces suicide risk, and that some clinicians feel pressure to support a medical pathway on the basis of reports that it does (paragraphs 15.36 and 15.43; same source). The report stresses that the distress of these young people is real.
The Swedish SBU concluded in 2022 that the scientific evidence is insufficient to assess the effects of puberty suppression and hormone treatment on gender dysphoria, psychosocial health and quality of life in adolescents (SBU). Since 2022 the Swedish Socialstyrelsen has recommended giving these treatments within a research setting and otherwise only in exceptional cases (source). The Finnish council COHERE wrote in 2020 that there is no medical treatment for minors that can be regarded as evidence-based, described gender reassignment of minors as an experimental practice, and allowed puberty suppression case by case after careful consideration (COHERE recommendation, unofficial English translation). The Norwegian commission Ukom advised in 2023 that puberty blockers and hormonal and surgical treatment of minors be classified as experimental treatment (source). In Denmark, Ugeskrift for Læger wrote in 2023 that the approach has become more cautious and that fewer young people receive hormone treatment (source). In England, NHS England decided on 12 March 2024 to no longer provide puberty blockers routinely (source), and in December 2024 the British government made the ban on the sale and supply of puberty blockers on private prescriptions to under-18s indefinite (British permanent ban on private prescriptions).
Puberty blockers are not a 'pause button'
Puberty blockers (GnRH analogues) were long presented as a pause button that gives a young person time to think. The Cass Review writes that by far the majority of young people who start blockers go on to masculinising or feminising hormones, that there is therefore no evidence that blockers buy time to think, and that there is concern that they may change the course of psychosexual and gender identity development (paragraph 83; source). In the Leiden cohort of the Dutch Protocol, 87 percent (125 of 143 young people) went on to start hormones; the authors point out that this may be because the eligibility criteria select young people who are likely to continue (Brik et al. 2020, PubMed). In the British early intervention study, 98 percent (43 of 44) chose cross-sex hormones (Carmichael et al. 2021, PubMed). Research by Amsterdam UMC showed that more than four in five referred young people began a medical pathway: 1,206 of the 1,470 young people referred between 2009 and 2019 (de Rooy et al. 2026, PubMed). Why, according to the site, the pause-button image is misleading is explained at puberteitsblokkers.nl.
On the physical consequences: the York review found lower bone density during treatment in several studies (source), and the Cass Review writes that the evidence on the effects on cognitive development and fertility is insufficient or contradictory (source). According to the Dutch Health Council, treatment with blockers in early puberty in trans girls in principle leads to infertility, unless they are willing to stop the blockers for a long period; according to the council, the effects on cognition and fertility have not yet been sufficiently studied (source).
Psychiatric comorbidity and the tendency toward a single explanation
According to the systematic review for the Cass Review, children referred to gender clinics have higher than expected levels of autism, ADHD, anxiety, depression, eating disorders, suicidality, self-harm and adverse childhood experiences (source). In the pooled studies, 9 percent of referred young people had an autism diagnosis (0 to 26 percent per study); see also eating disorders, autism spectrum disorder and ADHD. Of the studies that reported on adverse childhood experiences, 5 to 19 percent found sexual abuse and 11 to 67 percent found maltreatment or neglect (same source). The Cass Review writes that for some young people it is likely that the stress of the teenage years is expressed as gender distress, for example alongside eating disorders or body dysmorphia, and recommends that care also assesses and treats those accompanying problems (same source).
The cognitive reality of the adolescent brain
According to the Cass Review, brain maturation continues until about the mid-twenties, and the prefrontal cortex, which deals with complex decision-making and impulse control, continues to mature through the twenties. The report also writes that a 15-year-old makes similar decisions to an adult in hypothetical situations, but in practice may show risky behaviour despite understanding the risks, and describes decisions about these treatments for children as 'uniquely difficult' (source). The Finnish COHERE wrote in 2020 that brain development continues until about age 25 and that this also affects the ability to foresee the consequences of decisions for one's later self (source). What parents should and should not do in the first weeks after their child says they are trans is explained at transkind.nl.